1. Field of the Invention
This invention relates to a zoom lens having an automatic focus detecting device contained therein.
2. Description of the Prior Art
In recent years, numerous automatic focus detecting devices have been proposed in the optical devices of photographic cameras or the like, and zoom lenses incorporating automatic focus detecting devices in the zoom lens structure are known.
Consider an auto focus zoom lens provided with an optical system discrete from a picture-taking optical system as an optical system for automatic focus detection. Also, consider a compact zoom lens which comprises two groups, namely, a first group of negative power and a second group of positive power, which cover a wide angle to a medium focus condition.
In constructing an auto focus zoom lens of the above-described combination, a focusing error occurs during a zooming operation for the reason set forth hereinafter unless the arrangement of the optical system for automatic focus detection satisfies certain conditions, and thus resultant photographs are out of focus. Moreover, this phenomenon occurs even in a zoom lens in which the automatic focus detecting device has no detection error.